package Cytoscape.plugin.BNMatch;

import javax.swing.*;

/**
 * This is the 3rd version of SwingWorker (also known as
 * SwingWorker 3), an abstract class that you subclass to
 * perform GUI-related work in a dedicated thread.  For
 * instructions on and examples of using this class, see:
 * <p/>
 * http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html
 * <p/>
 * Note that the API changed slightly in the 3rd version:
 * You must now invoke start() on the SwingWorker after
 * creating it.
 */
public abstract class SwingWorker
{

    private Object value;  // see getValue(), setValue()

    /**
     * Class to maintain reference to current worker thread
     * under separate synchronization control.
     */
    private static class ThreadVar
    {

        private Thread thread;

        ThreadVar(Thread t)
        {
            thread = t;
        }

        synchronized Thread get()
        {
            return thread;
        }

        synchronized void clear()
        {
            thread = null;
        }
    }
    private ThreadVar threadVar;

    /**
     * Get the value produced by the worker thread, or null if it
     * hasn't been constructed yet.
     */
    protected synchronized Object getValue()
    {
        return value;
    }

    /**
     * Set the value produced by worker thread
     */
    private synchronized void setValue(Object x)
    {
        value = x;
    }

    /**
     * Compute the value to be returned by the <code>get</code> method.
     */
    public abstract Object construct();

    /**
     * Called on the event dispatching thread (not on the worker thread)
     * after the <code>construct</code> method has returned.
     */
    public void finished()
    {
    }

    /**
     * A new method that interrupts the worker thread.  Call this method
     * to force the worker to stop what it's doing.
     */
    public void interrupt()
    {
        Thread t = threadVar.get();
        if (t != null)
            {
            t.interrupt();
            }
        threadVar.clear();
    }

    /**
     * Return the value created by the <code>construct</code> method.
     * Returns null if either the constructing thread or the current
     * thread was interrupted before a value was produced.
     *
     * @return the value created by the <code>construct</code> method
     */
    public Object get()
    {
        while (true)
            {
            Thread t = threadVar.get();
            if (t == null)
                {
                return getValue();
                }
            try
                {
                t.join();
                } catch (InterruptedException e)
                {
                Thread.currentThread().interrupt(); // propagate
                return null;
                }
            }
    }

    /**
     * Start a thread that will call the <code>construct</code> method
     * and then exit.
     */
    public SwingWorker()
    {
        final Runnable doFinished = new Runnable()
        {

            public void run()
            {
                finished();
            }
        };

        Runnable doConstruct = new Runnable()
        {

            public void run()
            {
                try
                    {
                    setValue(construct());
                    } finally
                    {
                    threadVar.clear();
                    }

                SwingUtilities.invokeLater(doFinished);
            }
        };

        Thread t = new Thread(doConstruct);
        threadVar = new ThreadVar(t);
    }

    /**
     * Start the worker thread.
     */
    public void start()
    {
        Thread t = threadVar.get();
        if (t != null)
            {
            t.start();
            }
    }
}
